A cage of this type described in U.S. Pat. No. 5,391,005 has an approximately M-shaped cross-sectional profile and comprises two side rings which are joined to each other by circumferentially equally spaced crossbars. The crossbars, which together with the side rings define pockets for the reception of the rolling elements, are divided into a number of sections, viz., two side sections, one center section and two inclined connecting sections, that is to say, they are bent inwards towards the center of the bearing to extend beyond the pitch circle. The outward and inward retention of the rolling elements is effected by the sections of the crossbars situated outside and inside the pitch circle, respectively.
In such needle roller cages, the length of the needle rollers and the width of the cage are matched to each other so that the needle rollers extend with their axial dimension almost from side ring to side ring to prevent the ends of the needle rollers from tilting out of the pockets. Under certain technical conditions, however, for example, in the case of large transition radii on stepped shafts, it can become necessary to equip such cages with shorter needle rollers because, otherwise, the needle rollers would come into rolling contact with the transition radii of the transition region of the shaft. But if such a cage is equipped with shorter needle rollers, these could eventually tilt over the crossbars and slip beneath the stamped retention elements and thus fall out of the pockets. In the state of the art, this is prevented by the fact that the end faces of the rolling elements bear against radially inwards directed convexities of the side rings.
A drawback of this cage is that the convexities permit only an insufficient contact of the end faces of the needle rollers. This is due to the fact that the convexities, because of their rigid connection to the side rings, do not comprise a plane-parallel contact surface, i. e. a surface contact is not possible between the convexity and the end face of the needle roller but, at the best, only a linear contact.